1. Field of the Invention
The invention is based on an injector for a fuel injection system for internal combustion engines, having a high-pressure connection, the high-pressure connection communicating with an inflow conduit via a bore.
2. Description of the Prior Art
Some injectors, because of their design, require a system pressure that is markedly less than the pressure Pcr in the common rail, that is, the injection pressure. For instance, in injectors with a piezoelectric actuator, to lengthen the stroke of the piezoelectric actuator and compensate for the temperature-dictated length, a hydraulic booster is used. To fill this hydraulic booster, a system pressure of up to 20 bar must be present in the injector upon starting and during operation. Furnishing the requisite quantity of leak fuel is accomplished either by internal leaks in the injector or from outside.
Since in some embodiments of injectors no internal leaks occur, until now in these embodiments the pressure has had to be furnished from outside via high-pressure lines. Such an embodiment, because of the high pressure level and the high operating temperatures is expensive to produce and is vulnerable to malfunction.
Another disadvantage of the system pressure supply according to the prior art is that the system pressure is adjusted by means of throttles with a constant flow rate. This kind of throttling requires a high driving capacity on the part of the high-pressure pump and reduces the efficiency of the engine accordingly.
From FIG. 13 of German Patent Disclosure DE 39 36 619, an injection nozzle is known that has a high-pressure connection; the high-pressure connection communicates hydraulically with an inflow conduit via a bore, and a conduit to the system pressure supply branches off from the bore, and a bush with a longitudinal bore is disposed in the bore. In this injection nozzle, the longitudinal bore is embodied as an inflow conduit for a control chamber. The inflow conduit is supplied directly via the bore with fuel from the high-pressure connection. With this arrangement, it is not possible to furnish a simple, operational reliable system pressure supply for an injector.
Nor is this possible with the prior art, German Published, Nonexamined Patent Application DE-OS 28 54 921 that is cited in DE 39 36 619.